Epitaxial 2D materials beyond graphene

Carsten Busse

(Universität Siegen, Germany)

Epitaxial growth under well-controlled conditions (ultra-high vacuum, single crystal substrates) is a highly suitable method to prepare novel 2D materials. On top of that, this environment allows the study of key material properties using surface science methods as scanning tunneling microscopy (STM).

Transition metal chalcogenides form a comprehensive family of 2D materials containing metals, semiconductors and insulators. For tantalum sulfide on Au(111), we find a rich phase diagram including the established 2H-TaS₂, a novel monosulfide (TaS) and even an exotic Kagome lattice. We trace the growth back to the nucleation stage, where we observe TaS₃-clusters as the origin of theses phases.

Group-IV-monochalcogenides (here SnSe) are structurally analogous to phosphorene, but the ionic character of their bonds gives them additional properties as ferroelectricity. For 2D nanostructures this built-in electric polarization strongly depends on shape, size and edge termination. We prepare monolayer islands of SnSe on graphene/Ir(111) and find a transition from fractal-dendritic to compact islands with temperature. The final equilibrium shape is strongly influenced by edge reconstructions.